This invention relates to systems and methods for exposing material on the periphery of a substrate.
In the manufacture of integrated circuits (ICs) and semiconductor devices, the process of spin coating is used to apply photoresist (resist) on semiconductor wafers. Spin coating places a wafer on a chuck, dispenses resist on the wafer, and spins the wafer to distribute a thin film of resist over the surface of the wafer. The centrifugal force distributes resist onto the periphery of the wafer, but some ICs and devices cannot be made in the periphery. In fact, wafer handlers, pick-and-place machines and wafer cassettes may contact the periphery, causing resist to peel off and contaminate the wafer.
To prevent these problems, systems have been designed to expose and remove the resist on the periphery. One system includes a chuck for rotating a wafer located below a non-rotating fiber optic emitting exposing light at the periphery of the wafer. A non-rotating sensor detects the wafer edge and sends signals to memory of a control system after traversing the edge of the entire wafer, a process referred to as wafer mapping. After wafer mapping, the control system sends signals based on the stored signals to a radial transport arm, which moves the fiber optic in the radial direction to control the depth of exposure on the wafer.
This system has several problems. The rotating chuck assembly can generate airborne particles, which contaminate the wafer, and heat, which impacts the wafer temperature uniformity. Wafer mapping requires additional time and thus reduces throughput. Further, failure to isolate the wafer from the heat generated by the lamp of the exposure source assembly and from the controller subjects the wafer to unnecessary heat and particle contamination.
An ideal system today should be able to accurately expose the periphery of different diameter wafer such as 200 mm and 300 mm with notches, clips, flats and/or edge irregularities, expose a predetermined width, such as from 0.5 mm to 10 mm from the wafer edge, have high throughput such as 100 or more wafers per hour, and make sharp transitions from exposed to non-exposed resist without varying the temperature uniformity in a contamination free environment. It should be easy to maintain, operate, manufacture, reliable, and compact.
The invention provides systems and methods of exposing the periphery of a substrate. In an embodiment, the system includes an exposure source coupled to a guide directing radiation to a wafer, an edge detector, a transport, a support, and a control system. The guide includes a fiber optic and/or an optical system such as a catadioptric optical assembly. The transport moves the guide along the periphery of the substrate during exposure. The transport may achieve this by radial and rotating mechanisms. In one embodiment, the rotating mechanism supports the radial mechanism supporting the guide and the edge detector. The edge detector sends signals to a control system, which processes the signals and controls the transport to adjust the position of the emitting guide when necessary to expose the periphery.
In other embodiments, the system includes an exposure source chamber, a process chamber, and a control chamber to isolate the substrate from particulate and thermal contamination. The rotating mechanism may include a drum to house the substrate and support the radial mechanism. The radial mechanism preferably supports a tracking exposure head holding the edge detector and the guide emitter adjacent the substrate. The rotating and the radial mechanisms move the emitter and the edge detector subject to guidance and stopping mechanisms. A fiber optic assembly preferably directs radiation from an exposure source to the wafer. The edge detector provides signals to control the tracking exposure head to adjust for edge irregularities.